How much do you know about the cause of rhabdomyolysis?

This is the 4675th article of Da Yi Xiao Hu

I recently saw a post on the Internet. The gist of it was that a junior high school student was punished by his teacher to do 200 squats. Two days later, he felt unwell while walking on the playground during physical education class. He was sent to the hospital and diagnosed with rhabdomyolysis. I believe everyone is familiar with the term "rhabdomyolysis". In July 2010, many cases of rhabdomyolysis suddenly appeared in Nanjing and other places. The clear cause of the disease has not been found. Later, it was suspected that it might be related to eating crayfish. Because crayfish is a favorite food of many people, this incident caused a relatively large response in society at that time.

First, let's understand what striated muscle is. There are three main types of muscles in the human body: smooth muscle, cardiac muscle, and skeletal muscle. Smooth muscle is mainly distributed inside organs, such as blood vessels, intestines, etc., and is not controlled by consciousness; cardiac muscle is muscle tissue unique to the heart; skeletal muscle is attached to the bones, and we can control the movement of muscles. Skeletal muscle and cardiac muscle are actually striated muscles, because they show light and dark stripes under a microscope, so named. The rhabdomyolysis we usually talk about refers specifically to skeletal muscle damage. The main feature of this disease is that skeletal muscle cells are destroyed and intracellular substances are released into the blood, causing a series of symptoms and complications.

Why does rhabdomyolysis occur? Current research believes that it is mainly caused by cellular energy depletion and direct damage and rupture of the muscle cell membrane. There are so many possible causes of rhabdomyolysis. There are four common causes, such as hypoxic injury, physical injury, chemical injury, and biological injury. In addition, genetic metabolic diseases can also cause rhabdomyolysis. The most common causes of rhabdomyolysis in adults are trauma and drugs, and one-third of rhabdomyolysis in children is caused by infection. In the United States, more than 25,000 cases of rhabdomyolysis are diagnosed each year. Considering my country's large population base, the number of people suffering from the disease each year will also be very large.

Rhabdomyolysis after strenuous exercise is very common, especially in hot and humid environments. For example, in this case, the student was punished to do 200 squats, which may be the main factor inducing muscle cell damage. As for the obvious discomfort of the student when walking in circles during physical education class, it may be just a coincidence. Perhaps the patient himself was already very uncomfortable, but still insisted. After walking, his physical strength further decreased, and he finally couldn't hold on. Walking in circles itself played the role of the last straw, but walking in circles itself is far from inducing rhabdomyolysis.

200 squats may not be a big deal for a well-trained athlete. But for a junior high school student, whether the amount of exercise is too much to cause rhabdomyolysis remains to be determined by medical experts. Even medical professionals like me dare not make a rash assertion. However, what is surprising is that the local education bureau leaders quickly judged that an incident that should have been judged by medical experts and was highly professional was a problem of teacher ethics, and suspended the teacher and principal involved. It is unclear whether the education bureau leaders are confident in their medical literacy, or are anxious to appease parents and pick on the weak.

We mentioned earlier that childhood rhabdomyolysis is often associated with infection, with 22.3%-60.5% of childhood rhabdomyolysis caused by infection, mainly viruses. Whether the student was infected with pathogens that are prone to rhabdomyolysis, such as influenza virus, parainfluenza virus, and norovirus before becoming ill has not been reported. Rhabdomyolysis caused by genetic metabolic abnormalities accounts for about 10%-15% of childhood rhabdomyolysis, mainly lipid metabolism abnormalities, sugar metabolism abnormalities, and mitochondrial oxidation abnormalities, which are mostly autosomal recessive inheritance. There are dozens of such diseases, which often require high-tech means such as gene sequencing to diagnose. Unless they are doctors who specialize in these diseases, even doctors in other specialties have very limited knowledge of this. In addition, other factors that cause childhood rhabdomyolysis include endocrine abnormalities, electrolyte disorders, and autoimmune diseases. Some scholars have found that 40% of rhabdomyolysis in school-age children is caused by immune diseases, and its specific mechanism is still under study. Exercise-induced rhabdomyolysis is common in adolescent children, and its occurrence may be related to CK-MB/ACE gene polymorphism.

The above contents are very complicated. I have said so much not to ask ordinary citizens to master these professional knowledge, but to hope that everyone will not confidently accuse this and that with just a little knowledge. The more you know, the more humble and cautious you should be. Regarding the child patients in the post, the truly serious and responsible attitude is to give them a complete medical examination to rule out some potential patients. Blindly and arbitrarily looking for scapegoats to appease the family members is not the right attitude to deal with the problem.

Author: Songjiang Hospital Affiliated to Shanghai Jiaotong University School of Medicine

Han Dan Wang Xuemin